Design of a Blowing Type Flow Treatment to Complement Casing Treatments for Compact High-Pressure Compressor Rear Stages

Abstract

Abstract A common way to increase the operating range of rotor tip limited compressor configurations is the application of casing treatments (CT). However, the resulting strengthening of the rotor tip flow is accompanied by a radial re-balancing effect in the compressor’s flow path. This effect weakens the hub regions downstream of the CT. Consequently, a premature compressor stall can occur near the compressor hub. This paper presents the numerical design efforts for a hub strengthening flow treatment to leverage the potential of CTs within a compact high-pressure compressor (HPC) rear stage concept. A baseline HPC stage with large rotor tip clearances and stage loading is used as a starting point. An increase in compressor operating range substantiates within the rotor tip critical baseline HPC as axial slot CTs are applied. However, a premature stall initiation at the downstream stator hub occurs due to the radial re-balancing effect caused by the CT. Hence, a blowing-type flow treatment (FT) is introduced to delay the formation of the hub corner stall. Different geometrical variations of this FT type are tested numerically via a design of experiments (DoE). Finally, URANS simulations utilize this FT together with CTs to assess the changes in compressor operating behavior. The simulations show an enhancement of the stator operability due to a delay of the onset of the hub corner stall. By applying additional FTs, the adverse effects of the CT on the downstream stator can be partially compensated, and the potential of the HPC design can be leveraged.